Rheology, Morphology and Thermal Properties of a PLA/PHB/Clay Blend Nanocomposite: The Influence of Process Parameters

Abstract

The effect of process parameters on the final properties of a poly-lactic acid (PLA) and polyhydroxybutyrate (PHB) polymer blend filled with nanoclays was evaluated. To this aim, the nanofilled blend was processed in a co-rotating twin screw extruder, considering three different screw profiles and different values of the screw rotation speed, and the thermal and thermo-mechanical properties of the so-obtained materials were investigated. Furthermore, XRD analyses, SEM observations and rheological characterization were exploited to infer the coupled effect of the process parameters and nanoclay presence on the microstructure of the filled blend. Preliminary thermodynamic calculations allowed predicting the preferential localization of the nanoclay in the interfacial region between the polymeric phases. The relaxation mechanism of the particles of the dispersed phase in nanofilled blend processed, by rheological measurements, is not fully completed due to an interaction between polymer ad filler in the interfacial region with a consequent modification of the blend morphology and, specifically, a development of an enhanced microstructure. Therefore, by varying the screw configuration, particularly the presence of backflow and distribution elements in the screw profile, high shear stresses are induced during the processing able to allow a better interaction between polymers and clay. This finding also occurs in the thermo-mechanical properties of material, as an improvement of storage modulus up to 20% in filled blend processed with a specific screw profile. Otherwise, the microstructure of filled blend processed with different screw speed is similar, according to the other characterizations where no remarkable alterations of materials were detected.

Improving the Thermal Behavior and Flame-Retardant Properties of Poly(o-anisidine)/MMT Nanocomposites Incorporated with Poly(o-anisidine) and Clay Nanofiller

“…It is extremely elegant and crucial for commercial reasons because the products can be prepared for less money, with a simpler process, and with less weight, even though it represents the possibility of achieving a significant increase in thermal stability by using only a small amount of MMT clay in the finished product [ 25 , 39 , 40 ]. According to the DSC/TGA measurements, the inclusion of dispersed MMT clay in the polymer matrix considerably improved the flame retardancy and thermal stability of MMT/POA clay nanocomposites compared with pure POA [ 41 ].…”

Characterization of Optimized Ternary PLA/PHB/Organoclay Composites Processed through Fused Filament Fabrication and Injection Molding

“…The pattern of the PLA-JD/PHB-J blend is similar to that of PHB-J, with a peak at about 2θ = 23 • , which could be attributed to the presence of the PLA-JD crystalline phase. This peak indicates that the addition of semi-crystalline PHB-J could improve the crystallinity of PLA-JD because it has been noticed in the diffractogram of fully crystallized PLA, suggesting that PHB acts as a nucleating agent in PLA [7,11].…”

“…Layered silicates, more commonly known as clays, possibly organo-modified to produce nanostructures, are commonly used in PLA-based polymer composites [9][10][11]. Organic modifications are the most used methods to improve the properties of layer silicate, allowing a better interaction with polymers.…”

“…Ammonium salts are the most commonly used modifiers [13,14], but other reactive modifiers, such as monomer units, free-radical photopolymerization initiators, and particularly epoxy reagents, are used to cure and reinforce epoxy resins [15]. In the case of the PLA/PHA blend, it is expected that the addition of organo-modified layered silicate (OMLS) in the blend could result in an improvement of Young's modulus and tensile strength [11,16]. In fact, organo-modified montmorillonite would promote the compatibility between both polymers and limit coalescence processes that could occur during the processing of based-additive manufacturing filaments.…”

Volume Change during Creep and Micromechanical Deformation Processes in PLA–PBSA Binary Blends

“…In any case, while different researchers have investigated PLA toughened with biodegradable rubber, in which they stated that certainly the size of the dispersed particles, together with the quality of interfacial adhesion, determines the final toughening effect in PLA [34][35][36][37][38][39][40], only a few papers studied the short-time creep behavior of PLA-based blends [41][42][43], and none of them addressed the issue of relating micromechanical deformation phenomena with volumetric dilatometric variations from creep tests. For this reason, in this work, measurements of the volume strain, using an optical extensometer, were conducted with a universal testing machine in creep configuration to determine, accompanied by SEM images, the micromechanical deformation processes involved in a biopolymeric blend system.…”